Glomerulonephritis and vasculitis caused by anti-neutrophil cytoplasmic autoantibodies (ANCA) Is the most common form of rapidly progressive glomerular disease. The objective of this competitive renewal is to improve the lives of patients with ANCA disease by elucidating the underlying immunologic and pathogenic mechanisms, and translating this knowledge into improved patient care. During the current Program Project, we have made substantial progress in a number of exciting avenues of exploration that will be pursued in four Projects and two Cores. Project 1 investigates epigenetic regulation of neutrophil genes, and genes that modify the phenotype of ANCA disease. Project 2 explores the biology of relapse and remission in a unique cohort of ANCA disease patients from the perspective of epigenetic regulation of autoantigen genes, B cell autoreactivity and T cell dysregualtion. Project 3 uses animal models of ANCA disease to study Involvement of the alternative complement pathway and Fcy receptors In pathogenesis. Induction of disease by different antigens, and the genetic basis for variations In disease severity. Project 4 provides translation of our more basic research Into clinical investigations to Improve ANCA disease outcomes. We will take advantage of our discoveries of pathogenic roles for epigenetic regulation and complement activation by treating patients with retinoic acid to alter myeloid gene expression and with antl-C5 antibodies to block complement activation. As an extension of the discovery of anti-plamsinogen antibodies while studying autoantigen complementarity, we will determine If venous thrombosis in ANCA disease patients is attributable to these antibodies. The Clinical Core is key to our studies and has allowed us to follow patients with ANCA disease for almost a quarter century. From this valuable patient cohort, we have obtained crucial clinical and pathological Information, and biological specimens. An Administrative Core provides underpinnings of our work. There is substantial synergy among all projects, each projects focus on ANCA disease from different perspectives, and the hypotheses can be tested In human and animal systems. Importantly, the lessons we are learning pertain not only to ANCA disease but also to autoimmunity and Inflammation in general.